Födinger Manuela, Veitl Mario, Skoupy Sonja, Wojcik Jadwiga, Röhrer Claudia, Hagen Wolfgang, Puttinger Heidi, Hauser Anna-Christine, Vychytil Andreas, Sunder-Plassmann Gere
Institute of Medical and Chemical Laboratory Diagnostics and Dialysis, Department of Medicine III, University of Vienna, Austria.
Kidney Int. 2003 Sep;64(3):1095-100. doi: 10.1046/j.1523-1755.2003.00173.x.
Transcobalamin II is a serum protein that transports vitamin B12 from the intestine to the tissues. This complex, holo-transcobalamin II, may reflect vitamin B12 availability in the body. Conflicting data exist with regard to the effect of a polymorphism in the gene coding for transcobalamin II, TCN2 776C>G, on transcobalamin II levels in the general population, which in turn may affect holo-transcobalamin II, vitamin B12, as well as total homocysteine (tHcy) plasma levels. The effect of TCN2 776C>G on vitamin B12 cellular availability in dialysis patients is unknown.
We examined the effect of TCN2 776C>G on holo-transcobalamin II, vitamin B12, and tHcy plasma concentrations in 120 dialysis patients.
Holo-transcobalamin II levels were normal or supranormal in all patients and showed a linear association with albumin (r = 0.205, P = 0.025) and with vitamin B12 (r = 0.778, P = 0.001), but not with age, creatinine, body mass index, tHcy, ln-tHcy, vitamin B6, plasma folate, and red blood cell folate concentration. TCN2 776C>G showed no effect on holo-transcobalamin II, vitamin B12, and tHcy concentration [one-way analysis of variance (ANOVA), post-hoc Scheffe test]. Multiple linear regression analyses showed that albumin and B12 are independently associated with holo-transcobalamin II, whereas TCN2 776C>G and MTHFR 677C>T had no effect. Independent predictors of ln-tHcy included creatinine, red blood cell folate, and the MTHFR 677TT genotype. There was also an effect of the TCN2 776CC genotype on ln-tHcy levels in this multivariate analysis, however, that deserves cautious interpretation because there was no effect of TCN2 genotypes by ANOVA and Scheffe test [median ln-tHcy concentrations according to TCN2 genotypes (micromol/L): CC, 3.22; CG, 3.30; GG, 3.23].
TCN2 776C>G does not influence holo-transcobalamin II or vitamin B12 levels, and has no major effect on tHcy concentrations of end-stage renal disease patients.
转钴胺素II是一种血清蛋白，可将维生素B12从肠道转运至组织。这种复合物，即全转钴胺素II，可能反映体内维生素B12的可利用性。关于转钴胺素II编码基因（TCN2 776C>G）中的多态性对普通人群中转钴胺素II水平的影响，存在相互矛盾的数据，而这反过来可能会影响全转钴胺素II、维生素B12以及血浆总同型半胱氨酸（tHcy）水平。TCN2 776C>G对透析患者维生素B12细胞可利用性的影响尚不清楚。
我们检测了TCN2 776C>G对120例透析患者全转钴胺素II、维生素B12和tHcy血浆浓度的影响。
所有患者的全转钴胺素II水平均正常或超常，且与白蛋白（r = 0.205，P = 0.025）和维生素B12（r = 0.778，P = 0.001）呈线性相关，但与年龄、肌酐、体重指数、tHcy、ln-tHcy、维生素B6、血浆叶酸和红细胞叶酸浓度无关。TCN2 776C>G对全转钴胺素II、维生素B12和tHcy浓度无影响[单因素方差分析（ANOVA），事后Scheffe检验]。多元线性回归分析表明，白蛋白和维生素B12与全转钴胺素II独立相关，而TCN2 776C>G和亚甲基四氢叶酸还原酶（MTHFR）677C>T无影响。ln-tHcy的独立预测因素包括肌酐、红细胞叶酸和MTHFR 677TT基因型。然而，在这项多变量分析中，TCN2 776CC基因型对ln-tHcy水平也有影响，但这一结果值得谨慎解读，因为根据ANOVA和Scheffe检验，TCN2基因型并无影响[根据TCN2基因型的ln-tHcy中位数浓度（微摩尔/升）：CC，3.22；CG，3.30；GG，3.23]。
TCN2 776C>G不影响全转钴胺素II或维生素B12水平，对终末期肾病患者的tHcy浓度也无重大影响。
